Microelectrochemical Flow Cell for Studying Electrocatalytic Reactions on Oxide-Coated Electrodes

Here, we report a new kind of microelectrochemical flow system that is well suited for studying electrode modifications, like thin films prepared by atomic layer deposition (ALD), that require substrates to have a two-dimensional form factor. The design provides a means for electrodes to be modified ex situ and then incorporated directly into the flow cell. The electrodes can be removed after testing and further modified or tested before being reincorporated into the flow cell. Using this cell, mass-transfer coefficients up to 0.011 cm/s and collection efficiencies up to 57 ± 10% have been achieved. Electrodes modified with an ultrathin layer of ALD Al₂O₃ and an overlayer of Pt dendrimer-encapsulated nanoparticles (DENs) have been incorporated into the flow cell and their electrocatalytic properties evaluated. Subsequently, the dendrimer was removed from the Pt DENs using a UV/O₃ treatment, and this provided direct contact between the Al₂O₃ layer and the NPs. Finally, the product distribution for the oxygen reduction reaction (water vs H₂O₂) was evaluated in the presence and absence of Pt–Al₂O₃ support interactions.